<template>
    <el-select :value="valueTitle" :clearable="clearable" @clear="clearHandle" style="width:185px;">
      <el-option :value="valueTitle" :label="valueTitle" class="options">
        <el-tree  id="tree-option"
          ref="selectTree"
          :accordion="accordion"
          :data="options"
          :props="props"
          :node-key="props.value"    
          :default-expanded-keys="defaultExpandedKey"
          @node-click="handleNodeClick">
        </el-tree>
      </el-option>
    </el-select>
  </template>
  
  <script>
  import { setTimeout } from 'timers';
  export default {
    name: "el-tree-select",
    props:{
      /* 配置项 */
      props:{
        type: Object,
        default:()=>{
          return {
            value:'id',             // ID字段名
            label: 'title',         // 显示名称
            children: 'children'    // 子级字段名
          }
        }
      },
      // /选项列表数据(树形结构的对象数组) 
      options:{
        type: Array,       
        default: ()=>{ return [] }
      },
      //初始值
      value:{
        type: String,
        default: ()=>{ return null }
      },
     //可清空选项
      clearable:{
        type:Boolean,
        default:()=>{ return true }
      },
      // 自动收起
      accordion:{
        type:Boolean,
        default:()=>{ return false }
      },
    },
    data() {
      return {
        valueId:this.value,    // 初始值
        valueTitle:'',
        defaultExpandedKey:[]    
      }
    },
    mounted(){
      setTimeout(()=>{
          this.initHandle()
      },500)
    },
    methods: {
      // 初始化值
      initHandle(){
        if(this.valueId){
          this.valueTitle = this.$refs.selectTree.getNode(this.valueId).data[this.props.label]     // 初始化显示
          this.$refs.selectTree.setCurrentKey(this.valueId)       // 设置默认选中
          this.defaultExpandedKey = [this.valueId]      // 设置默认展开
        } 
        this.initScroll()
      },
      // 初始化滚动条
      initScroll(){
        this.$nextTick(()=>{
          let scrollWrap = document.querySelectorAll('.el-scrollbar .el-select-dropdown__wrap')[0]
          let scrollBar = document.querySelectorAll('.el-scrollbar .el-scrollbar__bar')
          scrollWrap.style.cssText = 'margin: 0px; max-height: none; overflow: hidden;'
          scrollBar.forEach(ele => ele.style.width = 0)
        })
      },
      // 切换选项
      handleNodeClick(node){
        this.valueTitle = node[this.props.label]
        this.valueId = node[this.props.value]
        this.$emit('getValue',this.valueId)
        this.defaultExpandedKey = []
      },
      // 清除选中
      clearHandle(){
        this.valueTitle = ''
        this.valueId = null
        this.defaultExpandedKey = []
        this.clearSelected()
        this.$emit('getValue',null)
      },
      //清空选中样式
      clearSelected(){
        let allNode = document.querySelectorAll('#tree-option .el-tree-node')
        allNode.forEach((element)=>element.classList.remove('is-current'))
      }
    },
    watch: {
      value(){
        this.valueId = this.value
        this.initHandle()
      }
    },
  };
  </script>
  
  
  <style scoped>
    .el-scrollbar .el-scrollbar__view .el-select-dropdown__item{
      height: auto;
      max-height: 274px;
      padding: 0;
      overflow: hidden;
      overflow-y: auto;
    }
    .el-select-dropdown__item.selected{
      font-weight: normal;
    }
    ul li >>>.el-tree .el-tree-node__content{
      height:auto;
      padding: 0 20px;
    }
    .el-tree-node__label{
      font-weight: normal;
    }
    .el-tree >>>.is-current .el-tree-node__label{
      color: #409EFF;
      font-weight: 700;
    }
    .el-tree >>>.is-current .el-tree-node__children .el-tree-node__label{
      color:#606266;
      font-weight: normal;
    }
  
    /* 开发禁用 */
    /* .el-tree-node:focus>.el-tree-node__content{
      background-color:transparent;
      background-color: #f5f7fa;
      color: #c0c4cc;
      cursor: not-allowed;
    }
    .el-tree-node__content:hover{
      background-color: #f5f7fa;
    } */
  </style>
  